US2424997A - Production of aviation gasoline - Google Patents

Description

PRODUCTION OF AVIATION GASOLINE Filed Oct. 21. 1942 a 3J5? E a =3 i g 3 a o J a E x a l E s (t k 1 3 5 x L Q I \j P Q] a a 0 a g E 9 E E E l Q \J E INVENTOR ROGERMNEWTON I BY ATTORNEY Patented 'Aug. 5, 1947 UNITED STATES PATENT OFFICE fl wers! 99 Ma n -Ke t n Berlin: G e n to H in Process .Oorporation. Wilmington,

not. i of nppllcatlonpctolie'r 2i, 942} 402,194

sirable hydrocarbon material s. includlm motor a ios-"szi fuels and especially base material for 1189111 I aviation engines including grade, as well as training and commercial Bradesot aviation gasoline. 1

A principal object of theinvention is to desirable aviation basematerialtmm cracked-bye drocarbons in the gasoline boiling range.- Another obiect is to produce aviation base stock for 100' octane fighting grade aviation gasolinev which will meet both lean mixture and rich mixture requirements. as in the present A. F. D.-.1Q- and tic-tests. Another object is to produce maximum yields-o! aviation base materialtrom cracked gasolines. still other objects will be apparent iromthe detailed description which follows.

While the present invention has application to conversion of all types of cracked gasoline; whether thermal or catalytic, in the production or aviation base stock. it should beunderstood that the better the cracked gasoline to begin vvvitln the greater benefits accrue from the useioi this imventlon. As a basis for discussion, theretore, it is desirable to consider the characteristics oigood cracked gasoline, such as produced by catalytically cracking heavier hydrocarbons over active catalytic material of the silica-alumina type. whether the catalyst be produced by chemical treatment of naturally occurring clays or by coboilingportion of the gasoline cut. namely Cs and 00. the 6's out boiling in the range of 85 to 120' l"; l nd th'ecs cut In the range of 120'. to 190 The oleflnsshould be removed, or converted to othermore desirable hydrocarboiling range. which can be efleoted' by rather mild-conditions of treatment.

' Thesg'reatest improvement in the cracked gasoprecipitation of silica-alumina compounds to produce synthetic catalytic masses. Analysis and study of the components of such a catalytically cracked gasoline having an end point of approximately 450" F. indicates that the olenns are generally undesirable because of low clear octane value and low lead susceptibility. -The naphthenic Cs's and Cs'S are in general acceptable as having a moderately high clear octane and excellent rich mixture characteristics, although of low lead susceptibility. Naphthenes of seven or more carbon atoms are undesirable due to low octane and low lead susceptibility. Isoparafllns are desirable from the standpoint of stability, lead susceptibility and high lean mixture rating. Straight chain paraflins are of low octane but fortunately are not present in appreciable proportions in catalytically cracked fuels. The aromatics ar in general good with respect to rich and lean performance. C1 aromatics being best, Ce next and the Ca's acceptable. The aromatics of C0 and greater are of lower clear octane, poor lead susceptibility and or only moderate rich mixture characteristics.

The oietlns occur predominantly in the low line-stock. especially-from thestandpoint of rich mixture performance, is to be eflected on the heaviernaphth'enes and aromatics which occur in thabread boiling rang'e or 180 to 500 F,, as. 'ionegampie in a 200 to 450" F. cut. By selecting (cut 0! this boiling range which may at times be extended profitably to include hydrocarbons boiling between and 500 F. and subjecting it to the action or a synthetic cracking catalyst of high activity and purity under severe or drastic operating conditions, such as temperatures of 820 to 950 h. and superatmospheric pressures up to pounds per square inch gauge and feed rates (liquid volume of charge per volume at catalyst per hour) of about .4:1 to 1:1, the highest grade of aviation base stock is produced. The resulting hydrocarbons in the boiling range of aviation gasoline, it originally from a catalytic cracking operation, will meet both A. F. D.-1C and 30 tests [1000 and 8-4 (or S-2)+ .25 cc. lead. respectively] with 4 cc. oi lead and no alleviate, hydrooodimer, or other special addition fluid, or with very little oi. the latter. The same treatment of a cut 0! the same boiling range derived from thermally cracked gasoline will produce aviation stock which readily meets commercial and training grade specifications with the addition of lead alone and usually with small amounts of lead, not exceeding 4 co. in other words, the base aviation gasoline produced from the drastic treatment of the 200 to 450 cut is of such high quality that it will stand considerable dilution by aviation cuts from straight run gasolines or from the front end cut of the originally cracked material which has been subjected to treatment for removal or conversion of the oiefins. in general, the imposed conditions are the more eiTective the narrower the boiling range oi the stock treated. Conversely. the broader the cut treated the more severe the treating conditions must be to produce the desired eiTect on any one compound or group 0! compounds. On the contrary, however, the presence oi a large proportion of oleflns, as by inclusion of the C5 and Cs cuts, limits the severity or treat possible due to the tendency of the oleflns to deposit coke on the 3 catalyst, thus overburdening the regeneration part of the cycle.

For a refiner to attain a maximum yield of high grade aviation gasoline from cracked hydrocarbons he should divide the motor fuel into two or more cuts for suitable treatment. The point or points of division focus around the Cu material in the boiling range of about 130 to 210 F. Hence, if he does not wish to make three cuts roughly asfqllgwse-thdCs's fise lii ifl 'ii, ,the

or 500 F). he can throw the Ca out either way,

the boiling range of 85 to about fl llli OIE -Wl th the heavier hydrocarbons to maize it out {if Co's to C'izs boiling from 140 to about;z4;,5lhto 500 EA other words the dividing lineiior thii tvi fiits' into which the hydrocarbon charge is divided iiiay be selected, as desired or as,-;to ur d ex;pedient, anywhere within a 100 range as from about 1'25" F. to about 225 F.

it a C cut is made ior ihe purpose oi producing alkylate, than. will be required to bring the remaining stock-aft r treatment to the proper boilingg angs. On the other hand, there is usually a shortage of iso-pentane and it is often desirable to treat the C5 out in a manner lo produce lso-pentane. To attempt to do this n Cs's alone involves difljic iltty since they 2:: s. "i. som sameness a. bottoms i g s' sa G t$Q8 in boiling inlthe range of 85- -tozabout.:200' I".

Is-pen an can. pggcdnced bp treating this cut no, ai mild cracking conditionmsuchzas temperatures oi 750 to 825 Ft,superatmospherio=pressure up to aboutv lbs. per square inch gauge, and

feed rates (liquid vclume-ot'charge per volume of catalyst. per hour) 01' 1:1 to 3:1 over a high activity catalyst of the silica-alumina type, preferably synthetically produced and 0t high purity, the operating periods not exceeding 30 minutes and being usually less than 20. minutes allowed by regeneration orthe catalyst. This treatment removes the olefins in the light out by converting them to more desirable hydrocarbons in the gas ollne boiling range. 1! production of iso-pentane is not required, other suitable or lower temperature treatments oi the light out may be utilized to remove the oleflns by polymerizing the same into higher boiling; hydrocarbons outside the aviation range and in the motor naphtha range or heavier. The high temperature treatment is usually preferable because it not only produces the iso-pentane but retains the material present as olefins in the aviation gasoline by converting them into more stable hydrocarbons.

It is im portantihat the original charge to the initial cracking step which precedes the cracked gasoline treatments contain no hydrocarbons boiling below the end point of the aviation gasoline which is to be produced. It is also desirable that the higher boiling out of cracked gasoline which is selected for drastic treatment, as in he 200 to 450 F. boiling range, below in oleflns since these are converted to coke and may unduly limit the onstream periods over the high activity Heating catalyst. For most operations the ole- Villa In this out should not exceed 10% either by Weight or volume.

In order to illustrate the invention and the mllliflfll' of its use one concrete embodiment oi nipnratus for conducting the entire operation. including the initial cracking step, is disclosed diagrammatically In the accompanying drawing.

The charging stock which may consist of crude hydrocarbons higher boiling than aviation gas oline is charged by line i to still 2 where the same is vaporized and sent under cracking con ditions to and through a reactor 3, which may be 0! any suitable or desired type, but it is preferably a catalytic reactor of either the static or fluid type charged with cracking catalyst of any known or desired type. The products of the cracking reaction pass by line 5 to iractionator isfor separation into a bottom or fuel oil out winch leaves the fractionator by line 6, a sidestream out which leaves by line I and an overhead cut which leaves fractlonator 5 by line 8.

overhead fraction comprising light hydro- 6 carbons through C5 or Cs passes through a condenser I and thence into a separator Hi from which fixed gases escape by line H, and water (if any be present) by line l2, and hydrocarbons by line II. The hydrocarbons pass through heater H and thence to a suitable reactor l5, prererabLv catalytic, where oleflns are removed by conversion or by polymerization, the products leaving reactor 15 by line ii. In the meantime. the next lighter hydrocarbons down to or through Ci: pass by line I through vaporizer l1 and thence into reactor II where they are subjected to drastic cracking conditions over high activity cracking catalyst, the products leaving reactor II by line IS. The products of reactors I5 and I. may be withdrawn separately through lines 20 and 2|, respectively, or they may be fed by lines 22 and 23 into the same iractionator 24. An overhead fraction, cut to the end point or the desired aviation gasoline, passes by line 25 through condenser 26 and separato 27 and thence by line 28 to storage at 29. A heavier traction such as motor naphtha with an end point of about 410" F., for example, leaves frac tionator 24 by line 30 as a side stream fraction passing through cooler 3| and thence into storage at 32. Higher boiling material which is highly aromatic in character and hence useful for solvent purposes, as fuel oil, or as cracking stock for producing more aromatics is withdrawn from the iractionator 24 by one or more side stream lines, such as 33, as well as by bottom line 34 leading to storage at 35.

It is to be understood that only the most essentlal pieces of equipment are indicated in the drawing and then only diagrammatically; auxiliary equipment such as pumps, heat exchangers, regenerating circuits, etc. are omitted since they are not necessary to an understanding of the invention. When static bed reactors are used in the catalytic zones at 3, I5 and I8, a sufiicient number of them may be provided to permit continuous operation.

Htigh activity catalysts can be produced from naturally occurrin silica-alumina or clay deposits by suitable chemical or other treatment and-can be utilized advantageously in both treating zones 15 and i8. However, it is preferable to use silica-alumina catalysts produced synthetically and of low alkali metal content, as for example in accordance with the disclosures of U. S. Patents Nos. 2,283,172 and 2,283,173 issued to J. R. Bates on May 19, 1942, because synthetic catalysts give higher octanes to the treated stocks than do the catalysts produced from cla Cracking catalysts other than silica alumina which give excellent results when used fo high temperature treatments in accordance with the present invention are highly active compounds 01 the following: sillca-zlrconia, silica-aluminazirconia, silica-alumina-beryllla, etc. The activ c eeses ity index of the catalysts'used should bo above about 35, which indicates ability toconvcrt to lighter products at least 35% of a standard refe ence stock such as East Texas gas oil under standard operating. conditions (see pagel, column 1, line 65 through line 39, column 2 of United States PatentNo. 2,341,216 Issued April 25, 1944 to A; G. 'Peterlun). Ingenerai, on th basls of the activity of the catalyst chosen for .the high 7 temperature treatment of the cracked hydroca1 bons in the boiling rangeoi about 130120. 500'. 1?. the operating conditions are made more drastic in temperature, pressure or rate. or in all these conditions, than if the identical catalyst were utilized for the initial cracking operation on fresh hydrocarbon charging stock. Pressure of at least 25 lbs". per square inch is utilized in the high tern conditions on: high activity (41 activity i dex:

synthetic silica-alumina catalyst.

with productsjof anormai c nl ytic cracking operation a refiner will usually find it to be desir- .able to divide the resulting 'debutanlzed-motor 'perature treatment of .depentanized cha r-gin;

stocks.

when oleiins are to be removed troni the light; out by polymerization rather than by high tempernturecon version, a. desirablemethod is a liquid phase catalytic treatment at relatively low temperatures and under suiilcient pressure to maintain liquid phase conditions, as in line with the teaching U. 5. Patent No. 2,273,038 issued February 1'7, 1942 to E. J. Hcudry' and J P. Daugherty, Jr. "The following examples give results typlcai'oj various aspects of the invention and show the large percentage of aromatics in the final avlation gasoline stock. 7

Example 1 A depentanized cracked gasoline in the boiling range of 125 to 400 F. was separated irom a cracking operation on 42-88% East Texas crude over synthetic catalyst. This cut was treated under severe conditions as follows:

Rate. W. 0.!511' Hiquicl volume of charge to volume of 7 catalyst per hour) Tempcraturew 850 F.

Pressure '50 pounds per square inch gauze (in-stream ncriocLv minutes Catalyst. High activity (39 activity index) synthetic silicaalumina 1 boiling range (90% at 305 F.) was 604% by volume of the charge to the operation and had :1 Reid vapor pressure of 5 pounds. The m-ninntio content of the dcpentanized aviation gasoline was 41.27,. by volume which was uuorcximniely 50% higher than the best present commercial practice with this type of crude as charge. lso-pentane was added to bring the aviation base stock to 7 ounds A. F. D.-1!f test on the 7 pound material after the addition of 4 cc.s of tetraethyi lead was 97.3 octnnc. A. F. li -RC test with the same quantity of iearl Have Sv-tZ/iccfs of lead. Aromatics in lzh '7 lb. Reid vapor prcsmrc a id lion'worn 351i hv volume A dcbutnnizeli mui'n' arm-line {mm M wnmal gasolineinto two fractions oflsubstantially equalvolum'e. The lower boiling cut bes'inning wlth;

Co's and with its endpoint runnins up'zto about 1225' F. l 'nzore' highlyoieflnic thanthe. heavier. "cut but contains no undesirable ,naphthenes. or aromatics and its paraflln content is substantially.

entirely brunch-chain. material. Thus insub stance it requires oniy'a relatively lightftreating operation tof-remove o convert the claims. The higher boiling-cut (initial 200 to 225 F. and end point 450 to 500' E.) is predominatelyv aromatic and low in'oleflns. It is unsatisfactory for inch-,-

sionin finished aviationfgasoline because of low 10 octane and poor-gumstablllty. Severe treatment of this material overcomes these deficiencies and is possible because of the low olefin content. This treatment is particularly effective because at the high partial 'pressure which can be obtained on a narrow boiling cut and results in the removal oi the olefins and naphthen'e's and conversion of the aromatics to more desirable aromatics from the standpoint of rich mixture per.- formance. The present invention discloses methods of produclng from cracked hydrocarbons aviation Leaso-- lines which meet present day periormfinccit'ests.

In many instances the treatments set forth he? in produce aviation gasolincs of very-high rich mixture performance as wcll as. meeting volatility requirements. With the addition 0L4 ccs oi lead and no alkyiate or otheraddition-agent A. I. D.-3C tests of S2+ 2 cc. lead have been cxceeded (note Example 1 above). East Texas stock has been used in the examples because it is one of the most diiiicult stocks from which to produce aviation gasoline of acceptable rich mixture rating. More naphthcnic stocks give better per-fortnance under both .10 andSC tests and higher yields as well.

It is well known that the 1C test is not an ac} curate index of the lean mixture performance oi a [uel in a full scale engine. In general a finished loci of the type heroin described having 8, 1C rating of about il'l will give a full scale lean mixture performance equivalent to that of a com plotely paraffinic ilxel having :1 1C rating of mu when the 3C rating of the former is of the order oi 82+! 5 cc. lead or more.

claim as my invention:

1. Process of making high quality aviation lmsv stock which comprises subjecting cracked hi'dl'ficm'bons ha ing an end point not exceeding about 5110' F'. in at least two cuts and under villi-rim: operating condition and separately to t'Lai-mtnl by wi h activity siiiciuus cracking catalysis the hravier the out the more severe the irvalmonh the temperalures of the treatments racing! in excess of F. but not in excess of 950 l"., segregating hydrocarbons inth'e aviation gasoline boiling range from the products of said treatments, and combining said segregated h!- ri 116 02750476- s= nature; the g" cutin tile-range or are censo s separatiupriom the products 'ot n thoboiiihgna'nge o 'ajiatibn' 'gasp e; esteem biaioeaaiaaateauiy p shahWWdiidiiW-bfiififlfifl} am a mlsctnrifimte ,c mmmmenei boiling uran tn' a ann ii w fl 1M P. infltheipfifluetamiiave mm filiifl ofaliproximately soc ia-strat m parts tlie'f-fdivibion hel er enacted in the mice oi 12!? 43 22st rerciatizvely mild catalytic cracking treatment,- s n; letting the higher bollingpart to the: action of high; activity siliclous= cracking catalyst under sevsretoperating conditions inchidiii'g' low ieed nt ttemperature above 820 F. but not above 950 Egandgsuneratmospheric pressure up to 150 lbs. sq. in. gaugeiand combining the products in the-11 111.118 range or aviation-gasoline from both treatingoperationa V i i 4i, In-the production of base stock the process of dividing a charge oi cracked hydrocarbons havingan end point of approximately 500 F. into two parts, the division being eifected in the range 01' 1251:0225 It. sub- Jecting the lower boiling cut to relatively mild catalytic. treatment by high activity sillclous cracking catalyst at superatmospheric pressure up to about 50 lbs. per square inch gau e in the temperature range of 750 to about 825 F; and at teed rates (liquid volume oi charge per volume of catalyst per hourioi 1:1 to 3:1 toremove or to convert oleilns, subjecting the higher bailing out to relatively severe catalytic treatment by high activity sllicious cracking catalyst at superatmospheric pressure up to about 150 lbs. per sq. in. gauge in the temperature range of 820 to 950" F. and at feed rates or .421 to 1:1, and combining the products in the boiling range oi aviation gasoline from both treating operations to obtain aviation gasoline capable oi meeting both lean mixture and rich mixture performance requirements.

5. Process as set forth in claim 4 in which the cracking catalysts comprise synthetically produced silica-alumina compounds of low alkali metal content with activity indexes 01' at least 35.

6. In the production of aviation base stock, the process comprising the steps of separating cracked gasoline having an end boiling point of the order or 450 F. to 500 F. into two parts, a lower boiling part having an end boiling point in the range of about 125 F. to about 210 F. and containing most of the oleflns, and a higher boiling part concentrated in naphthenes and arohigh quality aviation matics but having a low content of oleflns,. subjecting said lower boiling part to catalytic cracking'treatment which increases its saturation by reducing its content of oleflns. improving said higher boiling partby subjecting it tocatalytic conditions which are suiilclently severe, including use'ci active silicious catalyst activity index of at least 35-5111 6 n o'spherlc and temperature within the range of 320 F. to 050' F., t client, transi'prmaiit v h a s nd a omat c into ni w within th aviation gasoline boilini range having improved rich mixture performance chap acterlstlcs. and combining products from both treat operations whichare in the boiling range ormsutn gasoline. 1. m the'pi'ojdi'lctlon of aviation base stock process steps of separating cracked anend point oi approximately 500" F. into twop'arta'the lower boiling part having an end boilihgpolnt andthe higherboiling an initial boiling point of approximately aoo'j n. redeem: the olefin content'oi said lower o 'r' bis ii e It to r t l m l al t cracking treatment. subjecting said boiling part to the action of a siiiclo'us catalyst of at least 85 activity index under severe cracking conditionc, and combining the products of the one:-

" ations on said lower boiling and higher boiling parts, which are in th boiling range or aviation gasoline.

8. In the production of aviation base stock the process steps 0! separating catalytlcally cracked hydrocarbons having an end point 01' approximately 500 F. into two parts, the lower boiling part having ,an end point and the higher boiling part anlnitial oi. approximately 200 F., convert- 1 ing oienns in said lower boiling part to saturates within the aviation gasoline boiling range by a REFERENCES CITED- The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,141,185 Houdry Dec. 27. 1938 2,161,676 Houdry June 0, 1939 2,242,553 Thomas et a1. May 20, 1941 2,287,940 McGrew June 30, 1942 2,300,240 Thomas Oct. 27, 1942 2,310,317 Roberts Feb. 9, 1943 2,313,117 Becker Mar. 9, 1943 2,276,081 McGrew Mar. 10, 1942 2,322,984 Watson June 29, 1943 2,323,756 Thomas Sept, 7, 1943 2,302,297 Connolly Nov. 17, 1942 2,333,625 Angeli Nov. 9, 1943 2,361,138 Vporhies, J1. Oct. 24, 1944 FOREIGN PATENTS Number Country Date 475,125 Great Britain Nov. 15, 1937

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